Point Transect Method

The point transect method is a technique based on point sampling to determine cover. To follow this method, point readings are taken at either systematic or random locations along a tape that is extended to create a transect across the site. A variety of devices, including sighting tubes, bayonets, and plumb-bobs have been used to ensure a vertical reading of the point through the tape.

The length and number of sampling points along the transect depend upon the vegetation, but it is usually more efficient to record more transects with fewer points per transect. Each transect is considered a sample unit, and summarized data from several transects are required for statistical analysis of cover data to compare differences among years or sites.

According to the objectives of the study, either ground cover, basal cover, canopy cover, and species composition can be determined by this method. Leaf area index can also be determined by recording all layers of the vegetation that are hit at each pin placement.

The point transect method is regularly used for rangeland inventory or monitoring purposes because it is easy to follow. Although it is a slower technique than the step point method, it eliminates much of the bias arising from subjective pacing. Using a tape instead of the point frame method is also less cumbersome in many vegetation types.

References and Further Reading

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Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Sons, New York, NY. pp 119-121.

Bureau of Land Management. 1996. Sampling vegetation attributes. Interagency Technical Reference, B.M./RS/ST-96/002+1730. pp 78-85.

Fisser, H.G., and G.M. Van Dyne. 1966. Influence of number and spacing of points on accuracy and precision of basal cover estimates. Journal of Range Management 19:205-211. (pdf)

Goodall, D.W. 1952. Some considerations on the use of point quadrats for the analysis of vegetation. Australian Journal of Scientific Research, Series B. 5:1-41.

Heady, H.F., Gibbens, R.P., and R.W. Powell. 1959. A comparison of the charting, line intercept, and line point methods of sampling shrub types of vegetation. Journal of Range Management 12:180-188. (pdf)

Poissonet, P.S., Daget, P.M., Poissonet, J.A., and G.A. Long. 1972. Rapid point survey by bayonet blade. Journal of Range Management. 25:313. (pdf)